Used primarily in the food industry as a preservative, especially in cured meats like bacon, ham, and sausages. It prevents the growth of harmful bacteria such as Clostridium botulinum, which causes botulism, and helps maintain the pink or red color of the meat during storage.

Also employed in industrial settings as a corrosion inhibitor in heating and cooling systems, where it protects metal components from oxidation and rust. It is added to antifreeze solutions and metalworking fluids for this purpose.

In medicine, sodium nitrite is part of a treatment regimen for cyanide poisoning. When administered with sodium thiosulfate, it helps convert hemoglobin to methemoglobin, which binds cyanide and allows the body to detoxify and eliminate it safely.

Additionally, it is used in research and chemical synthesis, particularly in diazotization reactions to produce dyes and certain pharmaceuticals.